According to StarTrek.com, Romulan Ale is “an infamous blue alcoholic beverage with a powerful kick, the drink has been banned in the United Federation of Planets since before 2285, and is still not a commonly known commodity.” It “was illegal because of a Federation trade embargo in the late 23rd century (as mentioned in Star Trek II: The Wrath of The Wrath of Khan and Star Trek VI: The Undiscovered Country) through the late 24th century (per Star Trek Nemesis). (SOURCE: Romulan Cuisine on Wikipedia)